Anti-reversion apparatus

ABSTRACT

An anti-reversionary device for installation into the intake or the exhaust of an internal combustion engine comprises an inner pipe substantially centralized in the conduit. A plurality of ports are formed in an annular wall extending between the inner pipe and the conduit. Slower boundary layer gas flow adjacent the conduit is directed through the ports, and accelerated to join the faster gas flow passing through the inner pipe. The annular wall is angled downstream from the inner pipe to the conduit with the ports forming gas flow-directing passages angled radially inwardly. The inner pipe and annular wall are supported in a cylindrical housing forming a unitary body fit to the conduit. One or more devices can be installed in the conduit.

FIELD OF THE INVENTION

The present invention relates to apparatus for affecting reversionaryflow characteristics in an internal combustion engine. Moreparticularly, a device is located in the intake or exhaust of an enginefor influencing gas and sound waves for improving engine performance.

BACKGROUND OF THE INVENTION

Intake and exhaust gas flow in an internal combustion engine is acomplex combination of pulsing high pressure and low pressure gas flowsand sound waves related to the cyclical action of pistons and the intakeand exhaust valves of the internal combustion engine. The interaction ofthe various flows can affect engine efficiency.

The gases are routed through intake and exhaust systems primarilycomprising a tubular conduit arranged to feed gases to the engine(intake) and extract gases from the engine (exhaust). Performance isrelated in part to the size of the conduit and the characteristics ofthe flow therethrough. As stated, the gas flow includes longitudinallypropagated sound waves which can aid or interfere with gas flow. Throughinteraction of the gas flow and sound waves it is possible to suffer areverse gas flow with an associated reduction in engine performance.

A variety of techniques have been proffered to suppress sound whilemaximizing engine efficiency. It is known to design anti-reversingexhaust systems which attempt to cancel reverse wave propagation.Factors include the size and number of conduits, devices insertedtherein and relative lengths, sizes and arrangements of componentsassociated therewith.

SUMMARY OF THE INVENTION

An anti-reversionary device is provided for positioning in the intake orthe exhaust conduit of an internal combustion, preferably substantiallyadjacent the cylinder head of the engine.

In one aspect, the anti-reversionary device is adapted to a conduithaving gas flow therethrough comprising: an inner pipe is positionedsubstantially concentrically within the conduit; and an annular wallextending between the pipe and the conduit, the inner pipe having atubular gas inlet projecting upstream from the annular wall forseparating the gas flow into a annular gas flow and a central gas flow,the central gas flow being faster than the annular gas flow at thetubular gas inlet, the annular wall having a plurality of ports formedtherein and about the inner pipe, the ports forming passages directedradially inward and downstream for accelerating the annular gas flow fordischarge into the central gas flow.

In another embodiment, the annular wall itself is angled downstream fromthe inner pipe to the conduit. In another embodiment, the inner pipe issuspended in a tubular housing by the annular wall, the tubular housingbeing adapted to fit into the conduit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross-sectional view of a gas flow conduit with aperspective view of an anti-reversionary device of one embodiment of theinvention fit therein;

FIG. 2 is a cross-sectional end view of the conduit andanti-reversionary device according to FIG. 1, viewed from the upstreamside of the device;

FIG. 3 is a partial section, cross-sectional view of one embodiment ofthe device of FIG. 1 detailing the inner pipe, one of a plurality ofannular wall ports and the gas flow therethrough;

FIG. 4 is a cross sectional view of a plurality of devices fit into aconduit;

FIGS. 5 a-5 c illustrate computer-generated flow simulations with andwithout an anti-reversionary device of the present invention, moreparticularly,

FIG. 5 a depicts the prior art conventional case of the flow velocity ofgas in a conduit without the device;

FIG. 5 b illustrated a form of anti-reversionary device which is modeledin FIG. 5 c; and

FIG. 5 c depicts the flow velocity of gas with the device of FIG. 5 b.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The anti-reversionary device of the current invention is adaptable toeither intake or exhaust system of an engine, both of which are subjectto the pulsating gas flow and sound waves inherent in a valved, internalcombustion engine. Herein, and as set forth in the examples below, thedevice is been described in the context of application to an exhaustsystem.

The intake, combustion and exhaust cycles of an internal combustionengine produce pulsating gas flows. In the exhaust gas flow, theproducts of combustion are typically expelled at about 300-800 feet perminute. Sound waves of the combustion process can travel at a nominal1500-1800 feet per second. The faster sound waves can form a partialvacuum zone into which the slower gas flow can be drawn, resulting inreversion. As known, reversion is detrimental to engine performance.

As known to those skilled in the art, flow through a conduit, includingflow through an exhaust pipe, is typified by a faster flow in a centerflow stream and slower flow along the conduit wall; the boundary layerflow. As shown in FIG. 5 a, the velocity adjacent the wall is slowerthan the velocity at the center, according to the well known velocityprovided in a pipe. The characteristics of pipe flow are used toadvantage in the present invention.

Turning to FIGS. 1 and 3, one embodiment of an anti-reversionary device10 for installation into the bore 11 of a conduit 12 comprising an innerpipe 13 supported substantially concentrically in the bore 11 is shown.The conduit 12 is connected to an internal combustion engine (notshown). Gas flow adjacent the center of the conduit 12 passes though theinner pipe 13. An annular wall 14 extends between the conduit 12 and theinner pipe 13. The inner pipe 13 has a tubular inlet 15 which extendsupstream of the annular wall 14 for separating the gas flow 13 into aslower annular flow 16 adjacent the conduit 12 and a faster gas flow 17more central to the conduit.

In some embodiments, the annular wall 14 may be affixed directly to theconduit 12. In other embodiments as shown in FIG. 3, the annular wall 14may be integral with a cylindrical housing 18 forming a unitary body ordevice 10, the housing 18 being sized to fit the bore 11 of the conduit12. Such as device is readily formed of sheet materials such as thosehaving a substantially uniform wall thickness.

Further, the annular wall 14 may be angled, forming a truncated cone. Asshown in FIG. 1, One embodiment finds the annular wall angled downstreamand radially outwardly from the inner pipe 13 to the conduit 12.

With reference to FIGS. 1-3, a plurality of ports 20 are formed in theannular wall 14 for the admitting slower gas flow 16 adjacent theconduit 12 upstream of the device 10 and directed discharge throughpassages 21 (best seen in FIG. 3) through the annular wall 14 to theconduit 12 downstream of the device 10.

The total cross sectional area of the passages 21 is somewhat less thanthe cross sectional area of the annular wall 14. One approach is tomaximize the cross-sectional area of the passages 21 within thecapability of conventional manufacturing techniques for the material ofthe wall 14. Slower annular gas flow 16 is accelerated through thepassages 21 to rejoin the faster central gas 17 downstream of the device10. Where the annular wall 14 has some thickness, the passages 21 can beangled somewhat to direct the annular gas flow 16 radially inwardly tothe faster central flow 17.

As shown in FIG. 3, the ports 20 form passages 21 which are angledthrough the annular wall 14. In one embodiment, the passages 21 areangled at about 20-30 degrees relative to the conduit 12, and parallelto a conduit axis A. Ports, can be spaced at equi-distancecircumferentially along the 360 degrees about the annular wall.Twenty-four circular ports 20 could be spaced at 15 degrees apart with aport diameter commensurate to having some supporting annular wall 14remaining between adjacent ports 20. In another embodiment, twenty-fourports 20 could be spaced at about 14.3 degree increments and atwenty-fifth port 10 at 17 degrees; there not being a fixed requirementfor specific spacing of ports.

As shown in FIG. 4, one or more of the anti-reversionary devices 10 canbe installed in a conduit 12.

EXAMPLE

For a conventional 2 inch outside diameter (OD) exhaust conduit 12having a 1.88 inch inside diameter (ID) in the bore 11, ananti-reversionary device 10 can be manufactured having a 1.5 OD tubularintake and a 1.37 inch ID. A housing 18 is sized with a 1.88 inch OD tofit the bore 11. The tubular inlet 15, inner pipe 13, annular wall 14and housing 18 typically have a {fraction (1/16)} inch wall thickness.The inner pipe 13 can extend about 0.43 inches upstream of the annularwall 14. The dimensions in the present example create a clearance aboutthe inner pipe 13; here being 0.25 inches measured between therespective ID's of the conduit 12 and the inner pipe. This clearanceaffects the slower annular boundary layer flow 16 adjacent the conduit12 for directed discharge into the faster central flow 17.

The annular wall is angled at about 45 degrees. Twenty-five ports 20,each about 0.125 inches in diameter are formed in the annular wall 14.Passages 21 are formed from each port 20 and through the annular wall14. In this example, the passages 21 are angled through the annular wall14 at about 26 degrees.

Turning to FIGS. 5 a-5 c, one can see the effect on the velocity of theexhaust gas flow. In FIG. 5 a, a computer simulation of the conventionalpipe flow in a conduit 12 is illustrated, having the slower boundarylayer flow 16 adjacent the conduit 12 and faster-and-faster flow as oneapproaches the center axis A. The simulation work was performed onsoftware entitled Ideal Flow Machine And Mapper developed by as providedby Virginia Tech, Department of Aerospace and Ocean Engineering,Blacksburg Va., USA and available athttp://www.aoe.vt.edu/˜devenpor/aoe5104/ifm/ifminfo.html.

An anti-reversion device 10 of the present invention and as shown inFIG. 5 b, was installed into the conduit 12. Once installed, a secondcomputer simulation was performed, as illustrated in FIG. 5 c. whichdemonstrates an increase in velocity of the slower annular or boundarylayer flow 16 to approach the faster central gas flow 17. Theacceleration of the slower annular flow 16 was achieved with little orno backpressure, typical of a standard venturi principle, and with asuppression of the environment which causes reversion.

Similar results can be obtained using scaled dimensions for thosedemonstrated above.

1. An anti-reversionary device adapted to a conduit having a borethrough which gas flow to or from an internal combustion engine,comprising: an inner pipe positioned substantially concentrically andco-axially within the bore of the conduit; and an annular wall extendingto fit between the pipe and the conduit, the annular wall having aplurality of ports formed therein and about the inner pipe, each portforming a passage directed radially inward and downstream and whereinthe inner pipe has a tubular gas inlet projecting upstream from theannular wall so that the annular wall separates the gas flow into aannular gas flow and a central gas flow, the central gas flow beingfaster than the annular gas flow at the tubular gas inlet, and theannular gas flow accelerates through the plurality of passages fordirected discharge into the central gas flow.
 2. The anti-reversionarydevice of claim 1 wherein the conduit is an intake to an internalcombustion engine.
 3. The anti-reversionary device of claim 1 whereinthe conduit is an exhaust from an internal combustion engine.
 4. Theanti-reversionary device of claim 3 wherein the anti-reversionary deviceis fit adjacent the engine.
 5. The anti-reversionary device of claim 1wherein the passages are angled radially inward at between 20 and 30degrees.
 6. The anti-reversionary device of claim 5 wherein each passageis angled radially inward at about 26 degrees.
 7. The anti-reversionarydevice of claim 6 wherein the conduit is the exhaust from an internalcombustion engine.
 8. The anti-reversionary device of claim 7 whereinthe anti-reversionary device is fit adjacent the engine.
 9. Theanti-reversionary device of claim 1 wherein the annular wall is atruncated cone which is angled downstream from the inner pipe to theconduit.
 10. The anti-reversionary device of claim 9 further comprisinga cylindrical housing adapted to fit to the bore of the conduit whereinthe truncated cone extends between the cylindrical housing and innerpipe.
 11. The anti-reversionary device of claim 10 wherein the housing,annular wall and inner pipe are formed as a unitary body formed of sheetmaterial.
 12. The anti-reversionary device of claim 11 wherein sheetmaterial has a wall thickness which forms the passage through theannular wall.
 13. The anti-reversionary device of claim 10 wherein thepassages are angled radially inward at between 20 and 30 degrees. 14.The anti-reversionary device of claim 13 wherein each passage is angledradially inward at about 26 degrees.
 15. The anti-reversionary device ofclaim 14 wherein the conduit is an exhaust from an internal combustionengine.
 16. The anti-reversionary device of claim 15 wherein theanti-reversionary device is fit adjacent the engine.
 17. A conduit fordirecting gas flow to or from an internal combustion engine comprisingone or more anti-reversionary device of claim
 1. 18. The conduit ofclaim 17 wherein the passages of each of the one or more devices areangled radially inward at between 20 and 30 degrees.
 19. The conduit ofclaim 18 wherein the annular wall of each of the one or more devices isa truncated cone which is angled downstream from the inner pipe to theconduit.
 20. The conduit of claim 19 wherein the each passage is angledradially inward at about 26 degrees.